Ignition control device



Nov. 2, 1937. c. L.. PRENTICE 2,097,776

IGNITION CONTROL DEVICE Filed July 25, 1935 5 sheets-sheet 1 Nov. 2, 1937. c. l.. PRENTICE 2,097,775

IGNITION CONTROL DEVICE Filed July 25, 1935 i 5 Sheets-Sheet 2 r1la 7.

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INVENTR r l CA/PLY/ E L. PRE/vT/CE B-g ATTORNEY f l. v. 1jr/A A.

Nov. 2, 1937.

Filed July 25, 1955 5 sheets-sweet 5 350 DEG/P556 of' CRAN/SHAFT Raffina/y INVENTOR CAR/.Y/.E L. PREA/77a Patented Nov. 2, '1937 1 UNITED STATES 2,097,776 IGNITION CONTROL DEVICEv Carlyle L. Prentice, New' York, N. Y.

Application July 25,

50 Claims.

The invention relates in general to an improved method in timing the spark discharge in the act of ring the combustion charge in the cylinder of an internal combustion engine employing the Otto 5 cycle and the invention relates to an improved form of ignition control system for such engines particularly in an automatically actuated timer control mechanism for use in practicing the method.

The primary object of the invention is to improve the operation of internal combustion engines with respect to the timing of the firing of the explosive mixture and thus improve the eiiiciency of such engine operation.

The present invention features broadly the time locating of the firing of the combustion charge relative to engine cycle movement, so'that by reference to a pressure time curve of combustion in the cylinder and with the timing of the ignition set at the optimum point the curve will cross the top dead center ordinate of the curve irrespective of its numerical pressure value but at that pressure for the time being which is equal to one-half of the pressure at the peak or maximum pressure indication of the curve. Diferently expressed, with the ideal ignition timing herein featured in order to obtain maximum efliciency, the top dead center ordinate crosses and is crossed by each and every pressure curve at the half peak pressure value point as the pressure is rising during the act of combustion.

Referring to the apparatus aspect of the invention, the primary object is to provide a simpliiied control for the timer of an ignition system which will automatically set the ignition at that point in the cycle of engine movement which will produce the most efficient combustion of the ring mixture in accordance with the principle just given, under the instant load and speed conditions present and-which will maintain the timing of the ignition as so set so long as the controlling condi.- tions in the combustion chamber prevail.

The method is practiced in the device disclosed herewith, as a preferred form vof mechanism for practicing the invention, in that means are provided whereby pressure criteria from the combustion chamber Of the engine at two succeeding points in the cycle are measured and compared automatically by the device itself, andthe ignition timing readjustrnents made automatically until the pressure criteria indicate that the ideal setting has been accomplished. VDescribed more in detail a measure of the combustion pressure condition is Vmade at the time the engine piston reaches the top of its travel or at upper dead cen- 1935, Serial No. 33,008

(Cl. 12B-117) ter; another measurement is made later as the peak pressure occurs at the termination of the burning of the charge, and, for ideal timing as above noted,r the second measurement should be exactly double the value of the rst measurement. Variations of these proportions as the engine controlling conditions vary thereafter cause an advance or retarding of the spark automatically until the rst and second measurements compare with the desired one-to-two ratio value and under which conditions the ring of the charge is properly timed. .Y

Still another object of the invention is to provide in the apparatus feature of the disclosure a simplified means for compensating for lag in the transmission of the pressures being measured through the different parts of the containing mechanism and thus avoid errors which might be' otherwise introduced by such lag in time of transmission of pressures from the engine cylinder to the mechanism controlled by such engine imposed pressure.

Still another object of the invention is to provide in the several control parts structures which float vor move freely on oil bearings and whichv are for the most part formed of movable parts light in weight and thus featuring the freedom of motion of the parts and the minimizing of inertia resistance to the transmission of the actuating oil pressures, and the avoidance of all Wear which can affect the adjustments of the device.

Various other objects and advantages of the invention will be in part obvious from a consideration of the method features of the disclosure and from an inspection of the accompanying drawings and in part will be more fully set forth in the following particular description of one method of practicing the invention, and the invention also consists in certain new and novel modifications of the preferred method and other features of construction and combinations of parts hereinafter set forth and claimed.

In the accompanying drawings:

Fig. 1 is a composite View showing parts of an internal combustion engine with a preferred embodimentgof the invention operatively associated therewith land with parts shown in vertical section;

Fig. 2 is a horizontal sectional View through part of the time control mechanism shown therebelow and taken inpart of the plane indicated by the line 2-2 of Fig. 1;

` Figs. 3 to 7 inclusive are transverse sectional views through the rotary distributing valve and associated parts and takenrespectively on the parallel planes indicated by the lines 3 3, 13 4, 5 5, 6 6 and 'I l, of Fig. 1, looking towards the left as indicated by the arrows; Fig. '7 showing the right hand end with the cover plate removed;

Fig. 8 is a fragmentary view showing a section through the free end of the rotary valve and coacting high pressure balancing vents;

Fig. 9 is a vertical sectional view taken axially of the rotary distributing valve in its position at top dead center of the engine piston and taken on the line 9 9 of Fig. 3 looking to the right as indicated by the arrows;

Fig. 10 is a View similar to Fig. 9 taken horiz'ontally through the axis of the rotary distributing valve and taken on the plane indicated by the line lll l0 of Figs. 3 to 6 inclusive and Fig. 9;

Figs. 11 to 14 inclusive are detailed horizontal sectional views taken through the cylinder body at the top of the engine cylinder shown in Fig. 1 and taken respectively on the lines Il l l, |2 l2, |3 |3 and I-Id of that figure looking in the direction indicated by the arrows;

Figs. l5 and 16 are exploded views of the rotary distributing valve assembly shown in perspective; Fig. 15 showing the valve and its telescoping balancing cylinder with parts of the latter broken away to expose the ducts and ports and Fig, 16 showing the balancing cylinder and its coacting telescoped end block and associated balancing chamber forming parts;

Figs. 1'7 to 21 inclusive illustrate a modified form of the rotary distributing valve'shown in the preceding gures;

Fig. 17 is an axial view in vertical section corresponding to Fig. 9 and showing a two part type of modified valve;

Fig. 18 is a right hand end view of the valve of Fig. 17;

Fig. 19 is an exploded view of the parts forming the fixed part of the valve and associated governor parts;

Fig. 20 is a plan view looking down on the shiftable valve part showing the movable top dead center port;

Fig. 21 is a fragmentary view ofthe cylinder bore showing the coacting fixed top dead center port; and

f Fig. 22 is an explanatory chart for use in describing the operation of the device with particular reference to the relation of the pressure discharge ports in their function of supplying pressure to the diiferential piston disclosed in Figs. 1, 2 and 9.

In the drawings and referring first to the parts of the internal combustion engine to which the inventive features are applied, there is disclosed an engine A represented symbolically by one of its cylinders B in which is sldably mounted a reciprocating engine piston C representedin the showing in Fig. 1 at its upper dead center and on the point of starting on its power stroke and forming between the piston and the upper end D of the cylinder a combustion space E. The engine is provided with a high tension ignition system F comprising a spark plug G threaded conventionally into the upper end D for firing the charge in the combustion space E and connected with the ignition distributor and timer H through a high tension lead I and driven in synchronous relation with the engine cycle through the ignition timer drive shaft J. The spark is advanced or retarded conventionally through the shifting of a Limer crank arm K through a pressure actuated .-d a hydraulically controlled system hereinafter described. Oil for operating the hydraulic pressure transmitting system is taken from the pressure lubricating oil system or line L of the engine and the crank arm K is actuated by a vacuum energized device operating from the negative pressure in the engine intake manifold M.

Considered broadly the hydraulic pressure transmission comprises a pressure receiving and measuring device 20 carried by the engine cylinder exposed to the combustion pressure in the chamber E of the engine cylinder and from which device oil under pressure from the cylinder is conveyed through the supply pipe 2| to a pressure distributing mechanism 22, including a rotary distributing valve 23 for timing the pressure measurements, and directing low pressure to the large end of a differential valvular control 24 whenever the piston C reaches its upper dead center preceding a power stroke and for directing pressure to an automatic high pressure feeding device 25, for directing the maximum pressure in the explosion chamber to the small end of the diiferential control 21% and said control in turn interpreting the two pressure measurement and thereby controlling a vacuum servo mechanism 26 energized from the sub-atmospheric pressure in the engine intake manifold M and connected to shift the crank arm K of the ignition control mechanism.

Referring first to the pressure receiving and measuring device 29 illustrated at the left of Fig. 1 and in section in Figs. 11 to 14, there is disclosed a cylinder body 2l having a reduced lower end threaded through the upper end D of the engine cylinder and provided with a bore 28 extending axially therethrough. The lower end of the bore is slightly reduced to form a valve head receiving shoulder 29 and in the lower end of the bore is reciprocably mounted a gas pressure receiving piston and valve 3D, the lower end of which is exposed to the pressure condition in the combustion chamber or space E. The upper end of the piston is enlarged and has a sliding but oil-tight iit in the enlarged portion of the bore 28 to form a head 3! adapted in the absence of pressure acting thereon from chamber E to rest on the shoulder 29, under the influence of pressure from engine oil system L. The cylinder body 2l is provided with two axially spaced ports 32 and 33. The upper port 32 forms a pressure oil intake port and is` uncovered by the piston head when in its lowermost position shown in Fig. 1. The lower port 33 opens into the lower end of the unreduced portion of the bore a little above the shoulder 29, and when the piston is elevated off the shoulder, constitutes a lubricant supply port for lubricating the lower end of the piston and for allowing oil to freely enter and leave the annular space above the shoulder as the piston reciprocates. In this way the piston moves freely without static friction and will retain the oil above it. The ports are connected by a common duct 34 which leads out through the top end of the cylinder body. A ring-like valve body 35 (see Figs. 11-13) is located on top of the cylinder body and is held in position by a screw cap 36 provided with a bore 3'! extending axially therethrough and in communication with the portion of the bore 28 above the piston. Bore 31 communicates at its upper end with supply pipe through a readily demountable but oil tight connection. Duct 3G is in open communication with the pressure lubricating oil system L through connecting oil pipe 38 and a bifurcated duct 39 in the stem 40 of the valve body 35. One branch of duct 39 is in open communication with t'he duct 34 `and the other branch opens past a ball check valve 4| into the bore 31. From this construction it is appreciated that oil from the system L is free to pass into the bore in the cylinder body through upper port 32 and hence into the supply pipe 2l so long as the piston valve is in the lowermost position shown in Fig. 1. Also, should back pressure in the system connected to pipe 2| become superior to the pressure in the bore of the cylinder body, piston 36 will be forced down to its shoulder and the oil will freely flow back into the oil system L through port 32.

When raised from its shoulder 29 piston valve 36 closes port 32 thus shutting off communication with the system L and under such conditions if the oil pressure from source L becomes superior to the pressure in pipe 2| the oil passes the ball check valve against the tension of its seating spring 42 and passes into bo-re 31 and hence into pipe 2| and bore 28, forcing piston 33 down to` its shoulder again. Spring 42 has a tension merely sufficient to seat its check valve when no oil is flowing through the valve. From this construction it is seen that oil pressure delivered to pipe 2l will reflect accurately the pressure in the combustion space E at any instant Whenever the combustion chamber pressure is superior to the pressure in the lubricating oil system L, since the net flow of oil through pipe 2l is zero, and the absolute flow at any instant is Very small.

It is also seen that the system L will supp-ly oil to bore 28, and hence to pipe 2|, Whenever piston 30 is subjected to pressures from space E which are less than the oil pressure in system L. Since such low pressure conditions exist in space E periodically at every intake stroke of engine piston C, bore 28, pipe 2i and the associated apparatus will be kept filled with oil at all times under positive pressure from system L.

The ignition distributor and timer H are supported on an extension 43 from a solid, rugged block casing 44. The end of the casing opposite the extension is closed by means of an end plate 45 secured in place by bolts 46. The block is drilled and counterdrilled therethrough adjacent its lower face to provide a stepped bore 41 forming cylindrical bearing for the rotary distributing valve 23. The block is also drilled with a relatively large bore 48 forming the vacuum servo cylinder for containing timer actuating servo mechanism 25 hereinafter described.

The bore 41 is counterb-ored twice to provide the end thereof adjacent the end plate 45 of maximum diameter to receive the balancing sleeve 49 of the high pressure nding device 25 and an intermediate portion of slightly smaller diameter to provide a Vbearing for the enlarged end portion 55 of valve 23, and a small diametered portion shown at the left of Figs. 9 and 10 to receive the reduced end portion 5l of valve 23. The reduced end portion 5I is connected by means of tongue and slot connections 52 with the hub of a miter gear 53 journalled in the reduced end of the bore 41 and meshing with a miter gear 54 secured to the shaft J as shown in Fig. 1. The miter gears provide a one-by-one ratio so that the valve 23 is driven through shaft J in synchronous relation to the engine cycle. In this respect it is understood that the structure is conventional Withshaft J driven from the engine crankshaft (not shown) and which crank shaft in turn is actuated by the engine piston C. The large portionr5 of valve 23 is provided adjacent its reduced end with an annular oil receiving groove 55. The large end 5U is drilled from its right hand end to form a chamber or bore 56 communicating at its inner end with the groove 55 through four radially extending short passageways 51. Groove 55 communicates with intake passage 58 extending from bore 41 through an adjacent side of the block. Oil is received into the bore passage 58 from supply pipe 2| tted to the block by means of a terminal fitting 59 engaging in the outer end of passage 58. The right hand end of the valve `23 forms an open end barrel so that the oil pressure in its bore will react against the fixed end plate 45 and thrust the valve as a whole to its left against end thrust bearing 6D thus tending to reduce frictional resistance to rotary movement of the valve in its housing. One side of the valve 23 is slitted radially to form a slot form of outlet port 6I hereinafter sometimes referred to as the mov# ing top dead center port.

The valve 23 is so intergeared through shaft J With the engine that port 6I in the showing in the form of the invention thus far described is in its low pressure discharge position as shown in Figs. 1, 4 and 9 when the engine piston C is at its top dead center position preceding every power stroke shown in Fig. 1. The right hand end 5E) of the valve 23 is intruded into and journalled in the balancing sleeve 49 and which in turn is journalled for limited rotary movement in the large right hand end of the bore 41. The space between the right hand open end of valve 23 and the end plate 45 is filled with a cylindrical block 62 secured to the end plate by bolts 63 and cooperating with the balancing sleeve 49 as hereinafter described.

Directly above the enlarged end of the rotary valve bore 41 the block casing 44 is drilled and counter-drilled to provide a differential valve bore 64 and the left end of which is closed by a cap 65. Slidably mounted in the bore 64 is a differential piston valve 66 the left end of which forms the controlling element of the differential valvular control mechanism 24 and the right end of which forms part of the vacuum servo mechanism 26. The valve includes a large diametered left end portion 61 slidably mounted in the enlarged portion of the bore 64 and a small diametered right end portion 68 slidably mounted in the Vsmaller portion of the bore. A short inclined passage 69 (see Fig. 9) in the block casing terminates at its inner end in a narrow axially extending long slot forming the outlet port 10 and sometimes hereinafter referred to as. the fixed top dead center port. Means are provided for receiving and storing the oil pressure directed into the left end of bore 64 Without immediate resulting motion of piston 66 by means of an air compressor. For this purpose large end 61 of the piston is formed as a hollow cylinder in which is slidably mounted a plunger 1l forming a small air compression chamber 12 between the plunger and the adjacent end of the cylinder. In this way the engine combustion chamber pressure is conveyed through the intervening oil column as discharged from the rotary distributing valve at the top `dead center of the piston as will be presently described and is stored at least momentarily in the compressed air chamber 12 without at once causing piston 66 to move.

From this construction it will be seen that at the point Where the engine piston is at the point indicated at Fig. 1, that is, at the beginning of the power stroke, the pressure in the combustion space E is transmitted accurately and substantially without loss, to the left end of the differential piston and acts thereon to force plunger 1I inwardly to compress the air in the chamber 12 and therethrough act on the valve 66 to move the same to the right when restraining conditions permit as shown in Figs. 1 2 and 9. The pressure at the beginning of the power stroke, that is, with the piston C in the position sho-wn in Fig. l, is thus elastically stored in the cylinder after ports 6I and 10 have relatively passed beyond their point of registry and is held for comparison with the high pressure imposed on the small end of the piston as hereinafter described.

Referring to the high pressure finding and comparing device 25 and particularly referring to the left end portion of the balancing sleeve 49 in which valve 23 rotates, the sleeve (see Figs. 15 and 16) is provided with a relatively short and quite narrow slit 13 which extends therethrough and is designed to register with the slit port 6| of the rotary valve to pass oil pressure outwardly through the sleeve 49 and is hereinafter sometimes referred to as the maximum pressure discharge port.

'I'he upper portion of the enlarged end of bore 41 containing that part of the sleeve 49 which contains discharge slit 13, is provided with an arcuate chamber 14 (see Fig. 5) which communicates through inclined passageway 15 with the right hand end of the enlarged portion of bore 64 as shown in Fig. 9 to act on the shoulder constituting the small area end of the differential piston. It is a feature of this disclosure that the exposed area at the large or left hand end of the differential piston exposed to engine pressure at the piston top dead center is twice that of the area at the small or right hand end formed by the shoulder exposed to the maximum engine pressure existing in chamber E. It is thus apparent that combustion engine pressure is transmitted to the right hand or small area face of the differential piston at a time controlled by the rotarially adjusted position of the sleeve 49. For instance, in the showing in Figs. 5, 6 and 8, the port 13 has been shifted slightly anticlockwise from the vertically extending position of port 6| so that ports 6I and 13 are brought into registry at a time subsequent to the time when the engine piston C is at its top dead center position, or, diiferently expressed, while the piston C is on its power stroke.

Sleeve 49 is capable of a slight angular degree of rotation necessary to function as hereinafter described through the agency of two pairs of balancing chambers formed at the right hand end of the cylinder. For this purpose the cylinder is provided with two axially extending extensions (see Fig. 16) at the end and which extensions form diametrically disposed segments 16 and 11 rotating about the periphery of block 62. Positioned at diametrically opposite points on the block are a pair of fixed segments 18 and 19 secured to the block 62 by pins 89 and with the fixed segments located between the movable segments 16 and 11. I'here are thus formed two pairs of balancing chambers, one pair of chambers 8l and 82 connected by passageway 83 (see Fig. '1) and acting to rotate the valve counterclockwise and another pair of balancing chambers 84 and 85 connected by passageway 86 and tending to move the cylinder in a contra or clockwise direction as viewed in Fig. '1.

Pressure is introducedinto the connected pair of chambers 84 and 85 from the bore 56 of the aogwve rotary valve 23 through the rst high-pressure port 81 (see Figs. 5 and 6) opening through the inner peripheral face of the cylinder 49 and, as seen from Fig. 15, adjacent the port 13. Port 81 leads to groove 88 formed on one half of the cylinder surface and discharges through port 89 into chamber 85. Similarly, pressure is transmitted from bore 56 into the connected pair of chambers 8l and 82 from the second high pressure port 90 positioned on the opposite side of port 13 from port 81, and similarly leads by groove 9| to port v92 opening into chamber 82.

It is a feature of this disclosure that the slots forming ports 81, 13 and 99 extend parallel to each other, are closely grouped together as particularly noted in Figs. 8 and 15, and that the maximum pressure port 13 is a little closer to the rst port 81 than to the second or subsequently opening port 98. In this construction it will be seen that sleeve 49 rotates at least slightly and the segmental chambers will be changed in volume in proportion to the sleeve rotation. Therefore as the valve 23 rotates during the power stroke of the engine, oil pressure is supplied successively to the ports 81 and 99 and the balancing sleeve will be caused to rotate to a position where the pressures received by port 81 and 98 are equal.

It has been found that greater flexibility of oil pressure transmission is provided where the balancing chambers are lled with entrapped air which is compressed and expanded as the oil pressures on the pairs of balancing chambers increase and decrease. It will be seen that balancing sleeve 49 acts as is hereinafter more fully described to find the maximum pressure in the engine cylinder so as to locate port 13 in position to receive such maximum pressure when discharged through the revolving port 6I and thus convey such maximum pressure through passageway 15 to act on the small end of the differential piston in a tendency to shift it to the left. The diierential piston will respond immediately to oil pressures imposed at its small end, being held in elastic pneumatic restraint at its large end by the air in chamber 12.

The differential piston in its axial sliding movement to the right and left under the forces imposed thereon from the low pressure acting on the large end of the piston and the high pressure acting on the small end of the piston in turn acts to control the negative pressure from the engine manifold M and positive atmospheric pressure which act in turn through vacuum servo mechanism 26 to control the timer H. For this purpose the small diametered right hand portion 68 of the dierential piston valve 86 is provided with a spool like extension 93 provided with two longitudinally spaced apart long annular passageways 94 and 95 forming a valve plug 96 therebetween. Mounted in the right end of Vacuum servo cylinder is a leather cup piston 91 normally urged to the left by a relatively strong spring 98 bearing in one end against the piston 91 and at the other end against the end plate 45. The 'space between the piston 91 and the wall 45 forms a negative or vacuum pressure chamber 99 open to the engine intake manifold M through passageway H98 drilled through the casing between the right ends of bore 48 and the portion of bore 64 which contains the right annular passageway. This passageway is in communication with the manifold M through continuation passageway I 0l and pipe |02. Mounted in the cylinder 48 is a second piston I 03 normally urged to the left by relatively light spring |04 positioned between the pistons 91 and |03 and located in an atmospheric pressure chamber |05 formed between the pistons and adapted to be exposed either to atmospheric pressure or to manifold vacuum through passageway |06 as controlled by valve plug 9S. Air vent |01 leads from passageway 95 to vatmosphere outside of the block as shown in Fig. 2. A long thin piston rod |28 is secured to the piston |23 and which extends through the end Wall m9 of the cylinder d8. The outer end of piston rod |68 is connected by means of a link HE) with the free end of crank arm K to rotate the same to the left or counterclockwise as indicated by the arrow in Fig. 2 in order to retard the spark and similarly to rotate the crank arm to the right or clockwise to advance the spark.

While the device is complete as thus far described, it is suggested that means be'provided to cause a retardation of the spark if detonation occurs in combustion chamber E because of the use of poor fuel or for any other reason. For this purpose a bore H is provided in the casing (see Fig. 3) which opens through duct H2 into oil pressure supplying groove 55 in the valve 23. A small needle valve piston H3 (see Fig. 1) is slidably mounted in the bore, is normally maintained on its seat H4 (see Fig. 2) by a backing spring l i5 retained in position by hollow screw plug H3. Passageway H1 leads from beyond the seat M to the large end ci' bore till. Screw plug HS is adjusted so that the tension of the spring H5 is just suicient to balance the maximum oil pressure produced by normal full load combustion against needle valve piston H3. It is appreciated that detonation involves a sharp rise of combustion pressure above the normal maximum and will cause valve i3 to be momentarily opened permitting oil from duct H2 to ilow into duct Hl and thus increase pressure on the large end of the diierential piston. This results in movement of the piston to the right and causes a retardation of the spark and this abnormal retardation will be continued until the detonation condition ceases.

Referring to the modied form of rotary distributing valve shown in Figs. 1'? toI 21, it will be understood that the Valve 23 of the form shown in the preceding figures is here divided into two parts, an axially fixed driving part H8 and a slidable driven part l I which rotates with the engine driven part H8 and is` also free to partake of a limited axial movement between the part i8 and the cylindrical block 62. The sliding part H9 is in the form ci a cylindrical hollow barrel having its right end open and its left end dened by a wall l2@ provided with holes |2| extending therethrough Vfor placing the interior of the barrel in iluid communication with the oil pressure receiving space |22 positioned between the wall l2@ and the adjacent end of the part HS. A compression spring 23 is positioned in this space and tends to force the wall |29 to the right. The sliding part H9 is turned from the Apart l I8 by means of a pair of prongs i211 and |25 which project through the wall on opposite sides of its axis. The prongs are iconnected at their outer end by a short shaft E23 held in place by a pair of caps |21' secured by screws |28. A pair of bell crank forms of centrifugal governors |29 and |3Q are pivotally mounted on shaft |26 and are each provided with a semi-spherical form of governor ball i3! and. with a roller |32. The rollers bear on a cam face |33 formed on the right hand side of the wall i2@ as shown in Fig. i7.

` It will be understood that with increase orf engine speed there will be a corresponding increase of rotary speedv of the distributing valve as a whole and that with increase of engine speed the governor balls |3| in their tendency toi fly outwardly away from eachother will tend to move .the wall |20 to the left and against the resistance of spring |23. i

In this modied construction the discharge slot in the rotary distributing valve corresponding to the slot 6| of Fig. 9 is formed in two parts, the one part |34 supplying the passageway 69 and being formed helioally with reference to the outer cylindricalV surface of the valve to form a curved moving top dead center port in distinctionirom the corresponding straight port at the left hand end of slot 6|. The portion of the cylinder wall in which this curved port 34 revolves is provided with a similarly curved xed top dead center port |35 opening into the passageway 69 rather than the axially extending port l0 as shown in Fig. 9.

In the showing in Fig. 22, there is disclosed a Cartesian coordinate chart with the ordinates marked in combustion chamber pressures and the abscissae marked in degrees of crank shaft rotation and denoting the angular area adjacent the top dead center position of the engine piston preceding its power stroke. The valve ports 70, B1, 13 and 90, shown as long narrow chart bars, similarly designated, are shown in their relative positions rst in full lines at one hypothetical position of sleeve 49. The chart bars and thus the ports which they represent are shown in connection with apressure curve a as charted under conditions when the engine is at full load with its ignition point adjacent the 345 ordinate and a pressure curve b when the engine is on a light load and under high speed conditions with the desired ignition point adjacent the 300 ordinate. The ordinates or the points of intersection of the pressure curves with the ports, as shown on the graph, indicate the oil pressures at these illustrated hypothetical positions which will be supplied through the revolving straight or curved top dead center and other ports as they rotate past their corresponding fixed straight or curved top dead center and other ports.

InV operation and assuming a cycle of engine movement starting rst with the piston C at its upper dead center shown in Fig. 1 and that through the means hereinbefore described in connection with the cylinder body 21 and its contained mechanism, pipe 2| and the parts connected therewith including bore 56 and passageway 69, bore 64 and grooves 88 up to the balancing chambers form a column of oil under whatever pressure may be imposed thereon by the pressure in the system L, then any pressure in the chamber E tends to lift the piston valve 30 and thus impose pressure through the oil col-umn whenever the rotary valve 23 is in position to permit the transference of this pressure past the valve. As noted before, whenever the valve 23 in its rotary movement reaches its position with its discharge passage 5| registering with port 1G and which, as previously noted, has been'set to reach this position when the piston C is in the uppermost position preceding the power stroke as shown in Fig. 1, the pressure in chamber E is transmitted to the large end of the diierential piston, and is elastically stored in the air compression chamber 12 to be compared later with the maximum pressure in chamber E at the end .0.. the burning of the charge in chamber E.

`relative positions indicated at L2.

Tracing the oilpressure movementthrough the finding and comparing device 25, it will be seen that as the valve 23 rotates and supplies oil pressure successively to the ports 87 and 90 in that order, sleeve 49 will be caused to rotate slightly one way or the other to a position where the pressures discharged through these ports` are equal. When the sleeve 49 has been thus rotatively balanced the high pressure port 'F3 will be located to register with the associated passage 6| at the proper time to receive and transmit to the small end of the diiferential piston the maximum pressure then existing in the engine cylinder. y Referring to the chart of Fig. 22 for a further description of the operation, two hypothetical positions L1 and I..2 are shown. Assuming sleeve 49 to be with its ports in the relative position indicated in the full line showing at L1 and that the engine is operating under light load and at high speed Aindicated by the curve b. Under these conditions port 'i3 is in advance of its maximum pressure receiving position and port 90 will receive oil at a superior pressure to that received by port 8l by an amount indicated by the ordinate distance c-d and the counterclockwise rotation of sleeve 49 will result. This counterclockwise rotation is indicated by movement of the ports to the right or approaching their When position L2 has been reached, it will be seen from the segmental crown of the curve b` formed above the chord e-f that ports 8'! and 90 are receiving equal oil pressures and port 13 is set to receive the maximum pressure, the ignition point set in the illustrated case being at 300 crank shaft rotation, and this is the ideal firing point for this particular light load and high speed condition of the engine.

If now, the engine is operating under full load condition, it will be seen from the full load curve a that in position I..2 ports 81 and 90 are subjected to a difference in oil pressure indicated by the length of the ordinate distance g-h which tends to cause rotation of the sleeve i9 in a clockwise direction, or motion of the ports towards the L1 position. When this L1 position has been reached, ports 8'! and 90 are again disposed to receive equal oil pressures as indicated by the segmental crown of the curve a formed above the chord zl-y', port 13 again receives the maximum pressure and rotation of sleeve i9 will be arrested, the ignition point being retarded from the 300 to the 345 position and held at this point so long as this current'pressure condition continues to exist in the combustion chamber. With this construction itis seen that sleeve :i9 will always automatically seek the position in which ports 8? and 90 receive equal pressures from the axial moving top dead center port, Within the mechanical limits of its rotative travel, and'hence willautomatically place port 73 at or closely adjacent to the point where it will receive the pressure maximum, regardless of how this point may shift due to changing engine conditions.

It is noted that port 'i3 is not exactly centered between ports 8l and 90. Port 'i3 is located to receive the maximum oil pressure between the two equal pressure points located by ports 81 and 90 and due to the skewed shape of the peak of the combustion pressure cLuve a slight displacement of port 'i3 closer to port 87 than to port 90 is necessary so that oil at the peak combustion pressure is supplied through port 13 to the small end of the diiclentalpston- It is a feature of this disclosure as previously mentioned that the area at the large end of the piston is double the area at the small end. Therefore, if the oil pressure introduced through the port 13 is less than double the pressure stored in the cylinder l2, the diiferential piston will be displaced towards the right thus advancing the spark and, if more than double, the air in the cylinder i2 will be further compressed permitting displacement of the diierential piston towards the left with a resulting retarding of the firing of the ignition spark.

Again referring to the chart in Fig. 22, it is seen that if either combustion curve is shifted to the right, indicating not enough spark advance, ports 87, 'i3 and 90 will follow the peak of the curve and the pressure received by port 13 will be more than double that received by port 10 and the differential piston will be forced to the left. Conversely if either curve is shifted to the left, indicating too much spark advance, port 'l0 will receive more than half the pressure received by port 73 and the differential piston will be forced to the right.

A motion of the dierential piston to the left admits suction between the piston 91 and 363 drawing piston |03 to the right and advancing the spark. Similarly, motion of the diiferential piston to the right admits air at atmospheric pressure between the pistons, allowing spring E04 to move piston |03 to the left and thus retarding the spark.

Heavy spring 98 and piston 97 act to change the spark timing instantly when changing the throttle opening. 91, varies with the manifold suction, which in turn varies inversely with tthe throttle opening, it is seen that when the throttle is opened, piston 9"! moves to the left under the inuenoe of spring 98 and forces piston |03 to the left thus causing f is to cause a retardation of the spark setting as soon as the engine is stopped and the manifold vacuum lost, thus preventing a condition of dangerous spark advance when restarting the engine.

The description of the operation thus applied to the basic structure applies equally to the modied form disclosed in Figs. 17 to 2l. The modiiied form of rotary valve disclosed in these iigui'es is particularly designed for installation in engines which operate at high speed and which vary over wide speed ranges under varying loads in their normal function. Rapidly changing pressure conditions in the oil column function as in a manner resembling that of a sound wave and are transmitted with adjusted and constant timelags like sound which may for practical purposes be regarded as constant. In the primary embodiment of the invention herein time lag would tend to de-synchronize the half pressure rise point (see Fig. 22) with the opening of the top dead center portl 'i0 causing the half pressure rise point to lag further and further behind the opening and closing of the ports as the engine speed increases, and this, of course, causes the condition of over advanced spark proportional to en- S-ince the position of piston gine speed. The action of the governors causes a lag in the opening of the top dead center port in direct proportion to the engine speed, the lag being equal to the pressure wave lag in the oil transmission system. By the use of the modied form of control, the top dead center port is set closely synchronized with the half pressure rise point of the pressure waves as they arrive at the valve. The valve is set originally so thatl the ports |34 and |35 coincide at top dead center when the sliding part H is at the right hand limit of its axial movement.

Speed rotation will cause a displacement to the left of the sliding part i9 and this will take port i3d away from port |35 but a slight further rotation of part H9 will cause |34 and |35 to again coincide. It will thus be seen that with increase of engine speed, the governors will cause a proportionate angular shifting of the registering of port |34 with port |35, thus providing the desired proportional lag of the ports to compensate for the inertia lag in the oil column.

By changing the strength of spring |23, or by changing the helical pitch angle of the coacting ports, the degrees of lag per R. P. M. can be changed as desired. i

It will thus be seen that I have provided a new and useful method and apparatus forl maintaining the spark advance of an internal combustion engine at a predetermined optimum position dependent upon pressures within the cylinder that compensates for variations in the operating conditions such as the speed and load of the engine.

I claim: Y

1. In the art of timing the successive rlrings of the combustion charge in the cylinder of an internal combustion engine employing the Otto cycle and wherein the load and speed may vary between successive rings of the charge,V the method which consists in varying the timing of the ignition point so as to be automatically responsive to variations in load and speed and wherein at each firing strok-e of the piston the charge will be ignited at that point in engine piston movement which will cause the peak pressure after the charge is red to be approximately equal to double the pressure at the instant of time when the engine piston is at thev top of its cycle of travel preceding its power stroke.

2. In the art of automatically varying the tming of the firing of the combustion charge in the cylinder of an internal combustion engine employing the Otto cycle, the method which includes at each movement of the piston on its successive ring strokes the step of so timing the firing of the combustion charge at any particular stroke under varying load and speed that the combustion pressure in the cylinder at the beginning of that explosion stroke will be equal approximately to one half ofthe maximum or peak pressure created by the actual burning of the cylinder charge during that power stroke.

3. In the art of timing the successive rings of the combustion charges in an internal combustion engine in which the load and speed may vary, the method which consists in automatically regulating the timing of firing of succeeding charges relative to crank shaft rotation to cause the peak or maximum pressure in the combustion chamber at any particular `firing stroke to be twice the minimum pressure when the engine piston is at its Zero or top dead center position preceding that particular power stroke.

4. In the art of timing the firing of the combustion charge in the cylinder of an internal combustion engine in which the load and speed may vary, the method which consists in measuring the pressure in the combustion chamber as the pressure is rising during combustion at the point where the piston is at its top dead center preceding its power stroke and regulating the-instant of firing of the closely related immediately succeeding charge or charges even under varying load and speed conditions to cause the peak pressure in the combustion chamber to be twice said measured pressure.

5. In a device of the class described, the combination with an internal combustion engine having an ignition system, of mechanism for controlling said system comprisinga hydraulic device comprising a support having an open end cylindrical bore, counterbored to provide a length of small diameter at one end, a length of large diameteruat the other end and a hinge of intermediate diameter therebetween, a rotary distributing valve operatively connected to rotate in synchronous relation` with the engine cycle and having one' end of reduced diameter rotatably mounted in the bore length of small diameter and having its other end of enlarged diameter rotatably mounted in the bore length of intermediate diameter and protruding therefrom into the bore length' of large diameter, a balancing sleeve rotatably mounted in the bore length of large diameter and having one end journalled on the protruding end of the distributing valve, and provided at its other end with a pair of `diametrically disposed and axially extending segmental extensions, a cylindrical block secured to the support fitted in said other end of the balancing sleeve and provided on diametrically opposites with segments fitting between the extensions and ccacting therewith to form two pairs of balancing chambers, the chambers of each pair being in fluid intercommunic'ation, said distributing valve provided with a bore adapted to contain a liquid exposed to the pressure conditions in the engine cylinder and an axially extending slit opening into the same, said support provided with a low pressure slit adapted to register with the slit in the distributing valve at one point in its rotary movement, said balancing sleeve provided with three closely positioned parallel slits circumferentially spaced apart and adapted to register successively with the slit in the distributing valve, ducts in the balancing sleeve placing one of the outer of said three slits in uid communication with one of the balancing chambers and the other outer slit in communication with the other balancing chamber andthe support provided with a high pressure slit adapted to register with the middle of the three parallel slits in the balancing sleeve, a differential piston having its large end in fluid communication with said low pressure slit and having its small end in fluid communication` with said high pressure slit, said large end containing an. elastic pressure storage means, andV means connecting said ignition system control'mechanism with the differential piston to be controlled thereby.

.- 6. In a device of the class described, the combination with an internal combustion engine having an ignition system, of mechanism for controlling said'system comprising a hydraulic device comprising a support having an open end cylindrical bore, counterborled to provide a length of small diameter at one end, a length of large diameter at the other end and a hinge of intermediate diameter therebetween, a rotary distributing valve operatively connected to rotate in synchronous relation with the engine cycle and having o-ne end of reduced diameter rotatably mounted in the bore length of small diameter and having its other end of enlarged diameter rotatably mounted in the bore length of intermediate diameter and protruding therefrom into the bore length of large diameter, a balancing sleeve rotatably mounted in the bore length of large diameter and having one end journalled on the protruding end of the distributing valve, and provided at its other end with a pair of diametrically disposed and axially extending segmental extensions, a cylindrical block secured to i the support fitted in said other end of the balancing sleeve and provided on diametrically opposite sides with segments tting between the extensions and coacting therewith to form two pairs of balancing chambers, the chambers of each pair being in fluid intercommunication, said distributing valve provided with a bore adapted to contain a liquid exposed to the pressure conditions in the engine cylinder and an axially extending slit opening into the same, said support provided with a low pressure slit adapted to register with the slit in the distributing valve at one point in its rotary movement, said balancing sleeve provided with three closely positioned parallel slits circumferentially spaced apart and adapted to register successively with the slit in the distributing valve, ducts in the balancing sleeve placing one of the outer of said three slits in fluid communication with oneof the balancing chambers and the other outer slit in communication with the other balancing chamber and the support provided with a high pressure slit adapted to register with the middle of the three parallel slits in the balancing sleeve, and a differential piston having its large end in fluid communication with said low pressure slitiand having its small end in fluid communication with said high pressure slit and containing an elastic pressure storage device in said large end.

7. In a device of the class described, the combination of an internal combustion engine, an ignition system therefor, mechanism including a diierential piston for controlling said system from the pressure conditions in the engine cylinder, said mechanism including a support having a low pressure vent open to the large end of the diiTerential piston, a rotary distributing valve jcurnalled in the support operatively connected to rotate in synchronism with the engine cycle and provided with a bore adapted to contain an actuating liquid exposed to the combustion pressure in the engine cylinder and provided with a slit opening from the bore and said slit registering with the low pressure vent when the engine piston is at its top dead center preceding its power stroke, a balancing sleeve rotatably mounted on the rotary valve and provided with three circumferentially spaced and closely positioned slits adapted to be successively brought into registry with the slit in the rotary valve as it rotates,

said balancing sleeve provided at one end with two extensions, means providing two ixed segments positioned between and coasting with the extensions to form two pairs of balancing chambers, ducts placing each pair of chambers in fluid communication with one of the outer of these three parallel slits, whereby succeeding pressures in the engine cylinder acting on the actuating liquid will tend to rotate the balancing sleeve to the point where the pressures passed through these two outer slits are equal, and said support provided with a high pressure vent open to the small end of the differential piston adapted to register with the middle of the three slits in the position set by the balancing chambers as the slit in the distributing valve passes the middle slit in the balancing sleeve.

8. In a device of the class described, the combination of an engine cylinder and a pressure lubricating system, a cylinder body secured to the engine cylinder and provided with an axially extending bore and having a side port opening into the bore, a valve body at the outer end of the cylinder body and a cap engaging the outer end of the cylinder body and acting to secure the valve body in place and provided with a bore extending axially therethrough, said valve body provided with a duct and associated conduits placing the oil system in open communication with the side port at all times, and provided with a duct containing a normally closed valve for placing the bores of the cylinder body and the cap in fluid communication with the oil system whenever the valve is forced into open position by superior pressure from said system and a reciprocating piston valve contained in the bore of the cylinder body having its lower end exposed to the pressure in the combustion chamber, controlling said port and disposed to open said port to the pressure from the oil system when the pressure from said system is superior to the pressure in the combustion chamber and to close the port when the chamber pressure is superior to the system pressure, and mechanism in fluid communication with the bore of the cap and actuated by the superior pressure in the combustion chamber acting through the reciprocating piston.

9. In a device of the class described, the combination of an internal combustion engine, an ignition system therefor, means for varying the timing of said system, mechanism including a hydraulic pressure transmitting device for controlling said time varying means from the combustion gas pressure in one of the engine cylinders, means for supplying a liquid under pressure to the device to form a solid liquid column in the device, a reciprocating piston having one end exposed to the pressure in the engine cylinder and acting to transmit said pressure to one end of the liquid column, means coacting with the piston for automatically intercepting fluid communication with said source when the cylinder pressure is superior to the pressure from said source and for automatically releasing pressure in the liquid column into the source whenever it is superior both to engine cylinder pressure and to the pressure from said source, and-said mechanism including a device at the other end of the liquid column and controlled by the pressure transmitted through the column and in turn controlling the action of the time varying means.

10. In an internal combustion engine, the combination of an engine cylinder having a piston, an ignition device therefor including a control for timing the device, pressure means for actuating the control including a differential valve, a hydraulic pressure transmitting device having a column of liquid therein, means for maintaining an initial and relatively low pressure on the liquid column, a reciprocating piston having one end exposed to the superior pressure conditions in the engine during combustio-n, and the other end exposed to the liquid column to transmit cylinder pressure thereto, a valve operating in lli) synchronous relation with cylinder piston movement to subject the large end of the differential piston to the pressure in the liquid column imposed thereon by the pressure in the engine cylinder at the instantaneous time when the engine piston is at its upper dead center preceding its power stroke, andmeans timed by the pressure in the engine cylinder and independent of cylinder piston movement for subjecting the small end of the differential piston to the pressure imposed on the liquid by the cylinder pressure at the instantaneous time when such cylinder pressure reaches its maximum.

11. In a device of the class described, the combination of an internal combustion engine, an ignition device therefor including a timer, means for varying the function of the timer, pressure means controlled by the combustion pressure in the engine for controlling said varying means, said pressure means including anfoil conduit containing a column of oil exposed at one end to the variations of pressure in the combustion chamber of the engine, two valves in said oil conduit, one of said valves constituting a rotary distributing valve rotating in synchronous relation to engine piston movement and provided with a passageway opening therethrough, and the other Valve constituting a differential valve, the large end of said differential valve exposed to that oil pressure discharged from the rotary distributing valve when the engine piston is at or adjacent the initial position of its power stroke, Ameans controlled by the rotary valve for exposing the small end `of the diiferential valve to the oil pressure at or adjacent its maximum during or following the ring of the combustion charge.

12. In a device of the class described, the combination of an internal combustion engine, an ignition system therefor, mechanism controlled by the combustion pressure in the engine cylinder and including a differential `piston for controlling said ignition system, said mechanism including meanscperating in synchronism with the engine cycle for exposing the large end of the piston to the pressure in the engine cylinder at the instant when the piston is at its -top dead center preceding its power stroke, means .for exposing the small end of the differential piston to the pressure in the engine cylinder when said pressure is at its maximum value, said last named means including balancing means exposed to pressures in the engine cylinder at two successive points during the engine power stroke and acting automatically when the pressures at said two points are equal to set the opening to the .small end of the differential piston approximately at the maximum pressure point therebetween, and the opposite ends of the differential piston having their exposed areas in the ratio of one to two whereby the `differential piston is set immovable when the maximum pressure is twice the pressure at the' aforesaid piston top dead center.

13. In a device of the class described, the combination of an internal combustion engine, an ignition system therefor, mechanism controlled by the combustion pressure in the engine cylinder and including a differential piston for controlling said ignition system, said mechanism including means operating in synchronism with the engine cycle for exposing the large end of the piston to the pressure in the engine cylinder at the instant when the piston is at its top dead center preceding its power stroke, means forV exposing the small end of the differentialV piston to the pressure in the engine cylinder when said pres,-

sureis at its maximumvalue, and saidflast named pressures at these points are equalto set the f' opening to the small end of the diierential piston approximately at the maximum pressure point therebetween.

14. In a device of the class described, the combination of an engine, an ignitionsystem therefor including a timera timer drive shaft and means for varyingthe timing ofthe action of the ignition, mechanism for actuating saidvarying means, said'mechanism providing a hydraulic pressure transmission for conveying combustion pressure in the engine cylinder Ato said actuating mechanism, valvular control means in the transmission including a rotary distributing valve driven from the timer drive shaft for' opening the pressure from the engine at 'four points 4and for intercepting the pressure transference therefrom at all other points, one of said points Vbeing when the engine piston is at its upper dead center preceding its power stroke, the other three opening at automatically adjusted later instantsAT of time during the engine power stroke, said valvular control means also including a diiferential piston having its large end open through the rotary valve to the engine pressure at the first of said four points, means automatically controlled by the pressures at the second` and fourth points for opening the small end of the differential piston to an engine pressure at the third point between said second and fourth points at or closely adjacent its maximum value, said maximums value being located between Values of equal lower pressures preceding and following it which arrest the limiting action of the control when so equally received at said second and fourthpoints.

15. In a device of the class described, the -coml bination of an internal combustion engine, an ignition system therefor, a -control for the ignition system and a differential piston for regulating the control, said piston having its exposed large end twice that of the small end, elastic means for storing at the large end of the piston a pressure equal to that in the combustion chamber of the engine cylinder at the instant of time when the engine piston is at its top dead center preceding its power stroke, and means operable during the succeeding explosion stroke of the piston for subjecting the small end of the differential piston inelastically to the maximum value of the combustion pressure developed in the engine cylinder during said explosion stroke whereby the piston is moved towards its large end whenever the maximum engine pressure is more than twice the pressure at dead center piston position and is moved towards its small end when the maximum engine pressure is less than twice the pressure at dead center position and remains stationary whenever the maximum engine pressure is twice that at dead center piston position.

16. Means for regulating ignition of the charge of an internal combustion engine comprising pressure-operated means, a diierential piston for controlling said means, fluid means to place the opposite sides of such differential piston in communication with the pressure within the combustion space of the engine comprising successively acting control devices, and means to actuate the latter at different points in the travel of the engine piston in its cylinder, said fluid means `cooperating with said last named means to act on the large end of the piston when the engine end of the piston when the engine pressure is relatively high.

17. The combination of an internal combustion enginehaving a cylinder and igniting means for the combustion charge therein, a pressure operated means connected with the ignition means to regulate the same, a pressure actuated control therefor and' liquid means for the transfer of pressure between said control' and the engine cylinder operable at a point between the beginning and end' of the buring of the combustion charge..

1 8. Mechanism forsettingthe ring point of an internal combustion Vengine cylinder to cause yit to fire at a point A,prior to the position of the V.engine piston at top dead center, comprising a ,control mechanism for` advancing and retarding jthe spark, a differential piston regulating said control mechanism andV having one end with twice the exposed area of the otherend, means `for exposing Vthe large end of the differential piston to the pressure in the combustion chamber of the cylinder at the instant the piston is at its top dead center position preceding its power stroke, andmeans for exposing the small end of; the differential piston'to the pressure in .the combustion chamber and at a point between twoequalV pressure conditions in said combustion chamber during and after the burning of the combustion charge.

'19, In an internal combustion engine, the combinationv of an engine cylinder provided with an engine piston, ignition ldevice-therefor including la timer, a drive shaft therefor andl mechanism for controlling the timer, a hydraulic pressure transmitting device for regulating said timer con- -trol mechanism and including a column of liquid .adaptedV periodically tobe exposed to the pressure in the combustion chamber of the engine cylinder land, acting to transfer said pressure to the timer .control mechanism and means including a rotary Adistributing Valve driven from the timer drive Vshaft for selectively transmitting through said liquid column the pressure in the combustion chamber at a definite point of piston position rduring the combustion stroke of the engine piston.

20. In an internal combustion engine, the combination of a timing device, a control therefor including a sliding valve adapted to be moved to :and from an operative position, hydraulic pressure transmitting means having one end adapted to be exposed to the pressure in the combustion chamber of the engine to receive the gaseous explosive pressure therein and the other end yexposed tothe sliding valve and acting to move-the same into its operative position whereby the timjing device control is in turn controlled indirectly by the gaseous pressure in the combustion `chamber acting means. Y, Y Y ,Y i 21. An ignition timer and controller therefor, and a shaft for actuating the controller in syn- .chronous relation to engine piston movement,

Ymeans for Varying the time relation between the engine cycle and the function of the timer and vincludinga displacement member movable in a ,pressure chamber and means including a rotary valve operated by the shaft for successively sub- Jecting opposite ends ofthe displacement member to engine combustion pressures occuring at -successive points during the combustion act, one

of said points being when the piston is at its upper dead center and the other when the combustionlpressure is atrits-maximum.

through a liquid in the hydraulic 2,097,776 pressure is'relat'ively low and to act on the small 22. In a device of the class described, the combination of an internal combustion engine, an ignition system therefor including a timer, a pneumatically operated device for controlling the timer, valvular means for controlling sai-d device, said valvular means including a freely floating valve, an oil chamber in which said valve is contained and means operable from the pressure in the combustion chamber of the engine and otherwise independent of the combustion gases for shifting said valve promptly in its oil chamber whereby thetiming of the ignition system is a function of instantaneous pressures in the'combustion Chamber of the engine.

23. In a device of the class described, the comdbination of an internal combustion engine, an ignition device therefor, a control for said device including a ,differential piston, mechanism acting in synchronism with the engine cycle for periodically exposing the large end of the differential piston to thatgaseous pressure in the engine cylinder at the instant the engine piston is at its high dead center position preceding its power stroke, means coacting with said mechanism and controlled by the pressure in the cylinder during the explosionstroke for locating the instant of time when the pressure has reached its maximum and for exposing said maximum cylinder pressure to the small end of the differential piston, whereby the differential piston is held in pneumatic balance and thus the ignition device set to function whenever the ratio between the low pressure at piston dead center and the maximum pressure, is the reciprocal of the ratio between the pressure areas at the large and small ends of the differential piston.'Y

24. In an internal combustion engine provided with an ignition system, means governed by cornbustion pressure conditions in the engine for automatically fixing the spark discharge time, said means including a differential valve controlled and balanced by oppositely directed succeeding pressures thereon from the engine immediately preceding and during the firing stroke,

and means acting synchronously with engine piston movement and acting when the piston is at or adjacent its upper dead center to expose the large end of the differential valve to the pressure in the engine at that time and'to expose the small end of the differential piston to the pressure condition in the engine when at or adjacent its maximum value. v

25. In a device of the class described, the combination of an engine cylinder, an engine piston,

an ignition system including a timer and pneumatically actuated regulating device for advancing and retarding the timer, including a controlling valve for said device, differential piston 'in turn controlling said valve, hydraulic means acting on the dierential piston therethrough moving said controlling valve and influenced periodically by the gaseous explosive pressures in the engine cylinder and timing means operating in synchronism with the engine piston move- Vment to expose the large end of the differential '4 tem to function at apre-set pressure conditionfin fithe firing stroke for detecting the maximum pressure therein and for simultaneously exposing the small end of the differential piston to said maximum condition when so formed.

27. In a device of the class described, the combination with an internal combustion engine and an` ignition system therefor including a timer, of a. control acting on the timer for advancing and retarding the timing of the ignition spark, said controlincluding mechanism for selecting a time at which to set the control when the pressure in the combustion chamber is that at piston top dead center, said mechanism including a column of oil exposed at one end to engine pressure, and means synchronized with engine piston movement to transmit to the control the pressure at the time the engine piston is at or slightly beyond its top dead center position and means controlled by the maximum pressure condition in the combustion chamber for transmitting the pressureI under such conditions to the control and Asaid mechanism also including means for balancing said transmitted pressures against each other and in balancing to advance or retard the timing of the ignition spark.

trol, mechanism including means governed by the speeds of the engine for transmitting to the controlfthat combustion chamber pressure which exists whenthe piston is at its upper dead center, and including means for transmitting to the control the maximum engine pressure developed during the firing stroke.

, 29. In a device of the class described, the combination` of a vacuum servo cylinder provided with a closed end, two pistons mounted in the `cylinder for reciprocating movement, a means for supplying engine intake manifold suction to the space in the cylinder between the closed end and the adjacentpiston and tending to move both pistons in the direction towards the closed end, a relatively strong spring between the closed end and said adjacent piston tending to move it in the contra direction away from the end, a relatively weak spring between the pistons tending to move the other piston likewise in the contra direction away from the said closed end, the space between said pistons adapted to be open to the relatively high external atmospheric pressure or to the intake manifold suction, a valve controlling the opening of said space between the pistons to the external atmospheric pressure or the said suction, and mechanism connected tosaid other piston and actuated by the movement of said other piston.

30. In an engine having an intake manifold, a cylinder and a cylinder piston, ignition means therefor including a timer mechanism actuated from the engine intake manifold and connected to the timer for retarding and advancing the time of firing the ignition spark, control means for said mechanism including a hydraulic pressure transmission exposed to and operatively controlled by the pressure condition in the combustion chamber of the cylinder and likewise independent of the gases in said combustion chamber.

31. In a device of the class described, the combination of an internal combustion engine, a pressure transmitting piston exposed to .the combustion chamber of the engine, an ignition device for the engine including a timer, a` control for advancing and retarding the timer, pneumatic means for supplying the energy necessary t0 actuate the timer control, a valve for controlling the actuation of said pneumatic means, hydraulic l' means including a liquid column disposed between said pneumatic control valve and the piston for transferring to said pneumatic controlling valve the gaseous pressure from the combustion chamber as transmitted through the piston.

32. In an internal combustion engine comprising an engine cylinder, a piston reciprocating therein and means for firing the combustion charge in said cylinder, said piston and iiring means `being operatively connected to re the combustion charge at that point in engine piston travel to cause the piston to be at its top dead center position when the pressure value in the combustion chamber is approximately equal to one half of the peak or maximum pressure of the combustion during the firing stroke of the piston.

33. In a device of the class described, the combination of a support provided with a cylindrical bore, means for placing pressure on a body Yof oil in said bore, a pressure distributing cylindrical valve mounted for rotary movement in the bore, said Valve being of two parts With one part axially fixed and the other part axially. shiftable, said other part comprising a hollow barrel open to the oil pressure in the bore and having a wall at one end adjacent the xed part, a spring between the parts tending to separate them, a pair of prongs secured to the fixed part and intruded through the wall to rotate the shiftable from the axially fixed part, a governor within the barrel pivotally supported from the prongs, and provided with rollers engaging a cam surface on the wall and acting under the centrifugal force of the rotating valve to move the shiftable partv against the tension of said spring, said support provided with a xed oil pressure discharge port opening into the bore and the barrel provided with a coacting port extending therethrough and disposed helically with respect to the cylindrical barrel and said ports registering at diierent positions of the valve controlled by the speed of the valve.

34. In a device of the class described, the combination with an internal combustion engi-ne and an ignition system therefor including a timer, of a control acting on the timer for advancing and retarding the timing of the ignition spark, said control including a hydraulic pressure transmission system open at all times to the pressure in the combustion chamber of the engine cylinder, mechanism for exposing the resulting hydraulic pressure to other parts of the control at two points in the travel of the engine piston on its firing stroke, said mechanism including a timing means driven from the -engine for exposing the ressure when the engine piston is at or adjacent its upper dead center and including means controlled by the speed of the engine for advancing or retarding slightly the exposing of the pressure in timed relation to the upper dead center piston position, and said mechanism also including other means for exposing the resulting hydraulic pressure to said other parts of the control when the pressure condition in the combustion chamber reaches its maximum value.

35. In a device of the class described, the combination with an internal combustion engine and an ignition system therefor including a timer, of a control acting on the timer for advancing and retarding the timing of the ignition spark, said control including a diiferential piston, an o-il pressure transmission system including a two part cylindrical rotary valve turning in synchronism with the engine piston, one of said parts mounted for axial movement relative to the other axially fixed part, the axially movable part provided with a movable top dead centerY port, a coacting iixed top dead center port for placing the oil pressure in communication withV one end of the differential piston and said ports adapted-when in registry to open the Voil pressure to one end of the differential piston about the time when the engine piston is at its top dead center, a governor controlled by the speed of the rotary valve for shifting the movable part axially and for a relatively short `distance towards the axially xed part, a spring tending to resist said governor controlled axial movement, the movable port extending helically with respect to the cylinder surface of its valve part and whereby with variations in engine speed the ports are relatively shifted to register at points in engine piston travel displaced from the position at which they register at piston upper dead center position.

36. In a device of the class described, the combination with an internal combustion engine and an ignition system therefor including a timer,vof Va control acting on the timer for varying the timing of the ring of the ignition, saidV control including a differential piston, a hydraulic pressure transmitting system for transmitting pressure from the combustion chamber of the engine at succeeding times during the travel of the engine piston on its firing stroke to opposite ends of the differential pistonsaid,transmission system including a rotary distributing valve constituting a timing device driven from the engine and having a port disposed at one point in its rotary movement when vthe engine piston is at its top dead center, a

Vcoacting port in iiuid communication with the large end of the differential piston, said ports being relatively adjustable, means controlled by Ythe speed of rotation of said rotary valve for automatically varying the point in valve rotation adjacent its position when the piston is at top center position at which the ports register and acting to delay registering at relatively high engine speeds and said hydraulic transmission system including means operatively controlled by the maximum pressure in the combustion chamber during the firing stroke for transmitting such maximum pressure to the small end of the differential piston.

37. Ina device of the class described, the combination with an internal combustion engine Y and an ignition system therefor including a timer, of a control acting on the timer for varying the timing of the ring of the ignition, said control including a differential piston valve, hydraulic pressure transmitting means for exposing the large end of the differential valve to the pressure in the combustion chamber of the engine at the point when the engine piston is at its top dead center preceding its power stroke, and means controlled by increase of engine speed beyond a pre-set speed for delaying the time of such exposing until the piston has progressed slightly on its ring stroke, and said hydraulic pressure transmitting means acting to expose the small end of the diiferential valve to the pressure condition in the combustion chamber at the point Where this pressure has reached its maximum value.

38. In a device of the class described, the combination with an internal combustion engine and an ignition system therefor including a timer, of a control acting on the timer for advancing and retarding the timing of the ignition spark, said control including a differential piston having its large end of twice the exposed area of its small end, means for exposing the large end to that combustion pressure which exists at top dead center position of the engine piston, valvular means controlled by the combustion pressures for automatically locating the point of maximum pressure and means for exposing the small end ofthe diiferential piston to such maximum pressure when its point has been so located by the valvular means.

39. In a device of the class described, the combination with an internal combustion engine and an ignition system therefor including a timer, of a control acting on the timer for advancing and retarding the timing of the ignition spark, said control including a differential valve, means controlled by the pressures in the combustion chamber of the engine at upper dead center piston position ,and the maximum pressure for setting the diierential valve in position to eilect a setting of the timing device to meet the normal operating conditions of the engine, and means operatively responsive to an abnormally high pressure condition in the combustion chamber for exposing such abnormally high pressure to the large end of the diierential piston to move the same in the direction to cause a retardation of the timing as long as said abnormally high pressure conditions continue to exist.

40. In a device of the class described, the combination with an internal combustion engine and an ignition system therefor including a timer, of a control acting on the timer for advancing and retarding the timing of the ignition spark, said control including a differential valve, means controlled bythe pressures in the combustion chamber of the engine at upper dead center piston position and the maximum pressure for setting the differential valve in position to effect a setting of the timing device to meet the normal operating conditions of the engine, and means operatively responsive to an abnormally high pressure-condition in the combustion chamber forexposing such abnormally high pressure to the large end of the differential piston to move the same in the direction to cause a retardation of the timing as long as said abnormally high pressure conditions continue to exist, and a spring controlled means tending to maintain said means -in an inoperative position during normal engine operation and responsive to abnormally high pressures in the engine to cause said means to become operative.

41. In a device o0. the class described, the combination with an internal combustion engine and an ignition system therefor including a timer, of a control acting on the timer for automatically advancing and retarding the timing of the ignition spark in response to variations of pressure inthe combustion chamber ofthe "engine, said control including'mechani'sm selectively "actuated by said pressure in the combustion chamber at two points during its piston travel, said mechanismlincludin'g a differential piston and a pneumatic reservoir'aotingat all times on one end of the piston, said pneumatic reservoir exposed to receive'and i store the pressure imposed thereon from the combustion chamber at one of said'two points, andv means for conveying tothe other end of the differential piston the pressure imposed thereon from the combustion chamber at the other of said two'points. l

42. In a device of the class described, the combination with an internal combustion engine and an ignition system therefor including a timer, of mechanism acting on the -timer for automatically advancing and retarding the timing of the ignition spark in response to variations of pressure in the combustion chamber of the engine, said mechanism including a controlling differential piston, elastic storage means acting at all times on the large end of the differential piston tending to move it in one direction, means for selectively exposing said elastic storage means to the pressure which exists in the combustion chamber at the instant in its cycle of engine piston movement when the piston is at its top dead center thereby to energize said elastic storage means and tend further to move the differential piston in said direction, and means for selectively impressing on the small end of the differential piston the subsequent pressure which is present in the combustion chamber when such pressure is approximately at its maximum value thereby tending to move the differential piston in the opposite direction against the resistance of the energized elastic storage means.

43. In a device of the class described, the combination with an internal combustion engine and an ignition system therefor including a timer, of mechanism acting on the timer for automatically advancing and retarding the timing of the ignition spark in response to variations of pressure in the combustion chamber of the engine, said mechanism including a controlling differential piston, valvular means operatively connected to the engine piston for exposing one end of the differential piston momentarily to the pressure existing in the combustion chamber at the time when the engine piston is at or adjacent its top dead center and for promptly intercepting the exposing thereby to trap the pressure in its action on the differential piston until the engine piston again reaches its dead center position, and valvular means operatively connected to the engine piston for exposing the other end of the dierential piston to the pressure in the combustion chamber at a point intermediate the periodic exposing of the differential piston to combustion chamber pressure by the rst named valvular means.

44. In a device of the class described, the combination with an internal combustion engine and an ignition system therefor including a timer, of mechanism acting on the timer for automatically advancing and retarding the timing of the ignition spark in response to variations of pressure in the combustion chamber of the engine, said mechanism including a controlling differential piston, valvular means operating in synchronism with engine piston movement for exposing one end of the differential piston to the instant pressure condition in the combustion chambers each time the engine piston is at its top dead center, means for maintaining said pressure inA its action on the differential piston during the interval between twosuc'ceeding exposures and valvular means coacting with the rst named valvular means for exposing the other end of the differential piston periodically to the maximum pressure conditions present in the combustion chamber at the times of said periodical exposing of the maximum pressures.

In a device of the class described, the combination with an internal combustion engine and an ignition system therefor including a timer, of control mechanism acting on the timer for automatically varying the timing` of the firing of the ignition in response to variations in pressure conditions in the combustion chamber of the engine, said mechanism including a differential piston, liquid pressure transmitting means between the combustion chambers and the large end of the dilferential piston to move it in one direction, a valvular control for said pressure transmitting means operating in synchronism with the cycle of engine piston movement for exposing the large end of the differential piston to the combustion chamber pressure which exists at the instant time when the engine piston is at its dead center position preceding its power stroke, a second liquid pressure transmitting means for exposing the small end of the differential piston to the gaseous pressure in the combustion chamber at a succeeding instant of time during the engine piston on its power stroke, and acting in a tendency to move the differential valve in the opposite direction, a second valvular means coacting with the rst valvular means and including a pair of closely positioned ports for opening the second liquid pressure means to the combustion chamber pressure at two quickly succeeding points in the engine piston travel on its power stroke whereby the volume of combustion chamber space is substantially the same at the times when the two ports are exposed to its continued pressure.

46. In a device of the class described, the combination with an internal combustion engine and an ignition system therefor including a timer, of a control acting on the timer for advancing and retarding the timing of the ignition spark, said control including a valve, means controlled by the pressures in the combustion chamber of the engine at upper dead center piston position and the maximum pressure for setting the valve in position to effect a setting of the timing device to meet the normal operating conditions of the engine.

47. In a device of the class described, the com' bination with an internal combustion engine and an ignition system therefor including a timer, of a control acting on the timer for automatically advancing and retarding the timing of the ignition spark in response tc variations of pressure in the combustion chamber of the engine, said control including mechanism selectively actuated by said pressure in the combustion chamber at only two points during its piston travel, one of said points coinciding with the piston at its top dead center position and the other point coinciding with the peak pressure in the cylinder.

48. In a device of the class described, the combination with an internal combustion engine and an ignition system therefor including a timer, of a control acting on the timer for varying the timing of thering of the charge under varying load and speed conditions, said control including means responsive to the peak pressure in the engine cylinder to locate the time of ring the charge suciently in advance of the point of peak pressure so as to bring the pressure when it reaches a predetermined fractional part of the peak pressure in synchronism with the position of the piston at its top dead center.

49. In the art of firing the combustion charge in the cylinder of an internal combustion engine operable under variations in load and speed, the method which consists in measuring the pressure lzof in the combustion chamber at its point of maximum pressure on each of a closely related group of power strokes and regulating the instant of ring of each charge after an initial ring to take place at a time interval suciently prior to the'instant when the piston is at its top dead center to cause the piston to be at such top dead center position when the pressure in the chamber is approximately one half of the maximum pressure developed during the immediately preceding group of power strokes.

50. In the art of controlling gas pressures in an internal combustion engine during the travel of the engine piston onits power stroke, the

method which consists in automatically coordi-r CARLYLE L. PRENTICE.

CERTIFICATE- OF CORRECTION Patent No. 2,097,776. November 2, 195'?.

CARLYLE L. PRENTICE.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 6, second column, line 5?,"or "tthe" read the; page 7, second column, line 57, claim 5, for the word "opposites" read opposite sides; andI that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the ease in the Patent Office. l

Signed and sealed this lst day of February, A. D. 19.38.

Henry Van Arsdale, (Seal) Acting Commissioner of Patents. 

